Gaseous fuel injector having low restriction seat for valve needle

ABSTRACT

An electromagnetically operable fuel injector for a gaseous fuel injection system of an internal combustion engine, the injector having a generally longitudinal axis. which comprises, a ferromagnetic core, a magnetic coil at least partially surrounding the ferromagnetic core and an armature magnetically coupled to the magnetic coil and being movably responsive to the magnetic coil. The armature actuates a valve closing element which interacts with a fixed valve seat of a fuel valve and is movable away from the fixed valve seat when the magnetic coil is excited. The fixed valve seat defines a central fuel opening and a generally annular groove adjacent the central fuel opening, the armature having a generally elongated shape and a generally central opening for axial reception and passage of gaseous fuel from a fuel inlet connector positioned adjacent thereto. The fuel inlet connector and the armature are adapted to permit a first flow path of gaseous fuel between the armature and the magnetic coil as part of a path leading to said fuel valve. A method of directing gaseous fuel through an electromagnetically operable fuel injector for a fuel system of an ? combustion engine is also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates to a compressed natural gas injectorwhich incorporates an improved low restriction valve needle seat tocontrol the fuel flow in the needle valve seat area.

2. Description of the Related Art

Compressed natural gas (hereinafter sometimes referred to as “CNG”) isbecoming a common automotive fuel for commercial fleet vehicles andresidential customers. In vehicles, the CNG is delivered to the enginein precise amounts through gas injectors, hereinafter referred to as“CNG injectors”. The CNG injector is required to deliver a preciseamount of fuel per injection pulse and maintain this accuracy over thelife of the injector. In order to maintain this level of performance fora CNG injector, certain strategies are required to help reduce theeffects of contaminants in the fuel and to control the flow of fuelthrough the injector.

Compressed natural gas is delivered throughout the country in a pipelinesystem and is mainly used for commercial and residential heating. Whilethe heating systems can tolerate varying levels of quality andcontaminants in the CNG, the tolerance levels in automotive gasinjectors is significantly lower. Accordingly, utilizing CNG in enginespresents problems unique to CNG as well as to the contaminant levels.

These contaminants, which have been acceptable for many years in CNGused for heating affect the performance of the injectors to varyinglevels and will need to be considered in future CNG injector designs.Some of the contaminants found in CNG are small solid particles, water,and compressor oil. Each of these contaminants needs to be addressed inthe injector design for the performance to be maintained over the lifeof the injector.

The contaminants can enter the pipeline from several sources. Repair,maintenance and new construction to the pipeline system can introducemany foreign particles into the fuel. Water, dust, humidity and dirt canbe introduced in small quantities with ease during any of theseoperations. Oxides of many of the metal types found in the pipeline canalso be introduced into the system. In addition, faulty compressors canintroduce vaporized compressor oils which blow by the seals of thecompressor and enter into the gas. Even refueling can force contaminantson either of the refueling fittings into the storage cylinder. Many ofthese contaminants are likely to reach vital fuel system components andalter the performance characteristics over the life of the vehicle.

In general, fuel injectors require extremely tight tolerances on many ofthe internal components to accurately meter the fuel. For CNG injectorsto operate on CNG while remaining contaminant tolerant, the guide andimpact surfaces for the armature needle assembly require certainspecifically unique characteristics.

The CNG injector is required to accurately inject metered pulses of fuelover the life of the injector. It is also necessary to be able tocalibrate the injector to a specific calibration. Before it is possibleto calibrate a CNG injector, the design must have solved many of thespecific problems inherent in using CNG, including higher fuel pressuresand needle lift when compared to a standard gasoline injector, chokedsonic flow, and pressure losses through the injector. For propercalibration of the injector, the two most important parameters whichrequire control are pressure upstream of the choked flow, and orificesize.

In addition, to problems of contaminants in gaseous fuels, otherproblems relating to flow conditions and pressure losses must also beaddressed. For example. whereas in a standard gasoline injector orificesize is a parameter that is controlled to extremely tight tolerances,pressure loss is a CNG, or other gaseous fuel, specific problem whichmust be considered in the overall design when using gaseous fuels insuch injectors. Nevertheless, pressure loss is a natural phenomenonwhich occurs as fluid flows through any system. As the velocity of thefluid is increased and the fluid is forced through tortuous paths thelosses can become quite substantial over the length of the path. Theselosses contribute directly to the loss of overall mass flow availablefrom the injector. Without proper control of the high pressure lossareas in the injector, static flows would be nearly impossible tocorrelate.

The CNG injector generally has sonic flow exiting the injector. Thisoccurs with CNG any time there is a 55% pressure differential across anygiven point in the system. While sonic choked flow is achieved, thedownstream pressure is no longer included in the mass flow function. Theonly variables which contribute to the theoretical mass flow in a chokedflow system are gas constants, upstream pressure, upstream temperature,and flow area. The gas constants for any given fuel passing through theinjector from the fuel rail will be constant from injector to injector,and at present the area for the orifice is controlled very closely forgasoline applications. This leaves pressure and temperature as potentialvariables. The fuel temperature will not vary significantly frominjector to injector due to the short time available for heat transfer.However, the pressure above the orifice is affected by all of the lossesthroughout the injector and may vary between injectors.

As the fuel flows from the fuel rail through the injector, each itemcomprising the flow path contributes to the total loss in pressure. Someof these losses are small and some are quite substantial. In the presentCNG injector art, the main fuel path consists of the filter, upper inletconnector, adjusting tube, armature, valve body, lower guide, lowerguide/seat masked area, needle/seat interface and lastly, the orifice.

The filter, upper inlet connector, adjusting tube, lower guide and valvebody account for a very small portion of the overall pressure loss inthe injector. The armature has a small intentional loss to allow forfaster breakaway and dampening during opening impact of the valveneedle. This leaves only the lower guide/seat interface and theneedle/seat interface as the main controllable limiting factors forcontrolling pressure losses.

Theoretically, the needle/seat interface can be controlled through seatangle, spherical needle radius and lift. An increase in lift wouldreduce the magnetic force of the solenoid coil and lengthen the openingtime and linearity of the injector. As the spherical radius of theneedle increases, it thereby increases the exposed area for a given liftwith the result that the net force of the gas pressure increases. Thisalso lengthens the opening time of the injector. Presently suchinjectors utilize a needle/seat angle of approximately 90°. If the seatangle is increased from the present 90° angle, the flow area exposed fora given lift also increases as long as the needle spherical radius ischanged to accommodate the reduced sealing diameter. This concept,although appearing relatively simple, has several serious drawbacks.

When the seat angle is increased, two problems occur. The first problemis that the increased seat angle is more difficult to grind on existingseat grinding equipment. A good compromise between grinding capabilitiesand design can be reached to reduce the effect of this problem. Thesecond problem is that the flow past the lower needle guide/seatinterface becomes pinched and the flow loss from this interface becomessignificant. The present invention provides significant flow controlwhile avoiding the loss of fuel flow through a novel valve structurewhich incorporates a novel valve needle seat.

SUMMARY OF THE INVENTION

An electromagnetically operable fuel injector for a gaseous fuelinjection system of an internal combustion engine is disclosed, theinjector having a generally longitudinal axis, which comprises, aferromagnetic core, a magnetic coil at least partially surrounding theferromagnetic core, an armature magnetically coupled to the magneticcoil and being movably responsive to the magnetic coil, the armatureactuating a valve closing element which interacts with a fixed valveseat of a fuel valve and being movable away from the fixed valve seatwhen the magnetic coil is excited. The fixed valve seat of the fuelvalve defines a central fuel opening and a generally annular grooveadjacent the central fuel opening, the armature having a generallyelongated shape and a generally central opening for axial reception andpassage of gaseous fuel from a fuel inlet connector positioned adjacentthereto. The fuel inlet connector and the armature are adapted to permita first flow path of gaseous fuel between the armature and the magneticcoil as part of a path leading to the fuel valve.

In a preferred embodiment an electromagnetically operable fuel injectorfor a compressed natural gas fuel injection system of an internalcombustion engine is disclosed, the injector having a generallylongitudinal axis, which comprises, a ferromagnetic core, a magneticcoil at least partially surrounding the ferromagnetic core, an armaturemagnetically coupled to the magnetic coil and movably responsive to themagnetic coil, the armature having a first upper end face and a lowerend portion. A valve closing element is connected to the lower endportion of the armature and is interactive with a fuel valve having afixed valve seat to selectively permit fuel to pass through the valveseat as the valve closing element is moved to a valve open position bythe armature. The fixed valve seat has a generally frusto-conicallyshaped portion surrounded by an adjacent circular shaped annular grooveto reduce the pressure differential occurring across the valve closingelement and the fixed valve seat upon closing the fuel valve. A fuelinlet connector extends in a generally longitudinal direction above thearmature and defines a path for fuel to enter the inlet connector and tobe directed toward the armature, the fuel inlet connector having alowermost end portion having a lowermost surface spaced above thearmature to define a working gap through which the armature is movable.The armature has a fuel reception portion for receiving fuel directedfrom the fuel inlet connector, and further defines a generally axialfuel passage.

A method of directing gaseous fuel through an electromagneticallyoperable fuel injector for a fuel system of an internal combustionengine is also disclosed, the injector having a generally longitudinalaxis, and including a fuel inlet end portion and a fuel outlet endportion. A fuel inlet connector is positioned at the fuel inlet endportion and has a fuel inlet end portion and a fuel outlet end portion.An armature is positioned adjacent the fuel outlet end portion of thefuel inlet connector, the armature being spaced from the fuel inletconnector to define a working gap to permit movement of the armaturetoward and away from the fuel inlet connector to selectively open andclose a fuel valve by providing upward and downward movement of a valveclosing element to selectively permit gaseous fuel to pass therethroughto an air intake manifold. The method comprises directing the gaseousfuel to pass axially through the fuel inlet connector, directing thegaseous fuel to pass from the fuel inlet connector to the generallyelongated central opening of the armature in an axial direction towardthe fuel valve, and providing an annular groove adjacent the fixed valveseat for reception of fuel so as to reduce pressure losses across thefuel valve during closure thereof. In particular, the fuel is permittedto enter in volumetric space adjacent the fuel valve to reduce thepressure losses thereacross during closure of the fuel valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described hereinbelow withreference to the drawings wherein:

FIG. 1 is an elevational view, partially in cross-section, of apreferred embodiment of a compressed natural gas injector incorporatinga valve needle seat constructed according to the invention;

FIG. 2 is an enlarged elevational cross-sectional view of the lowerportion of the injector of FIG. 1, showing an enlarged view of the valveneedle seat shown in FIG. 1;

FIG. 3 is a partial elevational cross-sectional view of the lower endportion of the fuel inlet connector of the injector shown in FIGS. 1 and2;

FIG. 4 is a plan view of the bottom surface of the preferred fuel inletconnector shown in FIGS. 1 and 2;

FIG. 5 is an elevational cross-sectional view of a preferred embodimentof the armature shown in FIGS. 1 and 2 and illustrating the improvedfuel flow paths resulting therefrom;

FIG. 6 is an elevational cross-sectional view of the upper portion of apreferred embodiment of the valve body shown in FIGS. 1 and 2;

FIG. 7 is an enlarged cross-sectional view of a valve needle seat of thetype presently used in such injectors, the valve needle being shown in a“valve open” position; and

FIG. 8 is an enlarged cross-sectional view of an improved valve needleseat constructed according to the present invention and as shown in theinjector in FIGS. 1 and 2, the valve needle being shown in a “valveopen” position.

FIG. 9 is view taken along lines 9—9 of FIG. 2, illustrating a preferredvalve needle lower guide having arcuately shaped fuel passage openings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1 there is shown a CNG injector which isconstructed according to the present invention. Injectors of the typecontemplated herein are described in commonly assigned U.S. Pat. No.5,494,224, the disclosure of which is incorporated by reference herein.Injectors of this type are also disclosed in commonly assigned copendingapplications; U.S. application Ser. No. 09/320,178, filed May 26, 1999,entitled Contaminant Tolerant Compressed Natural Gas Injector and Methodof Directing Gaseous Fuel Therethrough, and U.S. application Ser. No.09/320,176, filed May 26, 1999, entitled Compressed Natural Gas InjectorHaving Improved Low Noise Valve Needle, the disclosures of which areincorporated herein by reference. Other commonly assigned, copendingapplications include U.S. application Ser. No. 09/320,177, filed May 26,1999, entitled Compressed Natural Gas Injector with Gaseous Damping forArmature Needle Assembly During Opening, U.S. application Ser. No.09/320,175, filed May 26, 1999, entitled Gaseous Injector withColumnated Jet Orifice Flow Directing Device and U.S. application Ser.No. 09/320,179, filed May 26, 1999, entitled Compressed Natural GasInjector Having Magnetic Pole Face Flux Director, the disclosures ofwhich are also incorporated herein by reference.

The injector 10 includes housing 12 containing armature 14 to whichvalve needle 16 is attached by crimping in a known manner. Fuel inletconnector 18 includes central fuel flow opening 13 and CNG filter 20 atthe upper end portion of opening 13 as shown. The fuel inlet connector18 also includes adjusting tube 22 connected thereto at 24 by a knowncrimping procedure. Housing 12 includes inner non-magnetic shell 26which surrounds the inlet connector 18 and armature 14 having centralfuel flow opening 11 as shown. Armature 14 and fuel inlet connector 18define with housing 12, an enclosure for solenoid coil 28 which isselectively energized to move armature 14 and needle 16 upwardly to openthe valve aperture 41, and selectively deenergized to permit armature 14and needle 16 to return to the “closed valve” position as shown, underthe force of coil spring 30. Fuel flow into the injector begins atfilter 20 and passes through fuel inlet connector 18, to armature 14,and ultimately to valve aperture 41 of valve seat 40 into the intakemanifold of the engine (not shown).

Referring further to FIG. 1 in conjunction with FIG. 2, valve body shell32, which is made of a ferromagnetic material and which forms part of amagnetic circuit, surrounds valve body 34 and has at the upper end,upper guide 36 as shown. Space 36 a between upper guide 36 and armature14 is about 0.010 to about 0.015 mm on the diameter, and permits guidingmovement of armature 14. Lower O-rings 38 provide sealing between theinjector 10 and the engine intake manifold (not shown) and upper O-rings39 provide sealing between the injector 10 and the fuel rail (also notshown). Valve body 34 defines central fuel flow opening 35.

In FIG. 2, valve body shell 32 is attached to valve body 34, preferablyby weld 32 a, and at the upper end by weld 26 a, to non-magnetic shell26. Non-magnetic shell 26 is in turn welded to fuel inlet connector at26 b. Thus, fuel flowing from fuel inlet connector 18 across working gap15 must flow through the clearance space 14 a between armature 14 andvalve body shell 32 which is also provided to permit upward and downwardmovement of armature 14. The space 14 a is approximately 0.10 to 0.30 mmon the diameter.

Referring again to FIGS. 1 and 2, valve seat 40 contains a valve orifice41 and a funnel shaped needle rest 42 having a frusto-conicalcross-sectional shape. The valve seat 40 is maintained in position byback-up washer 44 and sealed against fuel leakage with valve body 34 byO-ring 46. Overmold 48 of suitable plastic material such as nylonsupports terminal 50 which extends into coil 28 and is connected viaconnection 51 to provide selective energization of the coil to open thevalve by raising the armature 14 and valve needle 16 against the forceof spring 30. Armature upward and downward movement is permitted byinterface space 15 (or working gap) between the inlet connector 18 andthe armature 14. The working gap is generally extremely small i.e. inthe order of about 0.3 mm (millimeters). Solenoid coil 28 is surroundedby dielectric plastic material 53 as shown in the FIGS.

In injectors of this type, the interface space 15 (or working gap 15)between the inlet connector and the armature is extremely small, i.e. inthe order of about 0.3 mm (millimeters), and functions relativelysatisfactorily with conventional fuels which are relatively free ofcontaminants such as water, solids, oil, or the like, particularly afterpassing through a suitable fuel filter. Accordingly, when the twosurfaces surrounding space 15 are in such intimate contact that theatmosphere between them is actually displaced in relatively significantamounts, atmospheric pressures acting on the two members actually forcethe two surfaces together. Any liquid contaminant present at thearmature/inlet connector interface would allow for the atmosphere to bedisplaced, thereby adversely affecting the full and free operation ofthe armature/needle combination.

When known injectors, which functioned at relatively acceptable levelswith relatively clean conventional fuels, were utilized with CNG,impurities such as oil or water at the inlet connector/armatureinterface produced a force of about 16.5 Newtons holding the armature tothe inlet connector. In comparison, the force provided by spring 30 isin the order of about 3 Newtons, thus fully explaining the erraticclosing of the armature/valve needle when the fuel utilized with knowninjectors is CNG. In particular, the 16.5 Newton force holding the inletconnector and armature together is due to the fact that the fueloperating pressure within the injector is about 8 bar (i.e. 8atmospheres) and this force of about 16.5 Newtons acts across the lowersurface area of the inlet connector 18, which is about 21 squaremillimeters (i.e. mm²). Thus a relatively minor slick of oil or otherimpurity within space 15 of a known injector will cause the inletconnector and the armature to become temporarily attached to each other,particularly due to the 8 bar pressure acting on the remaining surfacesof the inlet connector and armature. As noted, the tendency for thearmature to become attached to the inlet connector results in erraticvalve closing.

The present injector eliminates the aforementioned erratic valve closingand improve the operation of the injector with gaseous fuels. In FIG. 3,the lower end portion of inlet connector 18 is configured as shown bythe arcuately chamfered end 52. This configuration provides a beneficialeffect in that it directs and orients the magnetic field across theworking gap 15 in a manner which optimizes the useful magnetic forcecreated for moving the armature through the working gap. This feature isdisclosed in commonly assigned application entitled Compressed NaturalGas Fuel Injector Having Magnetic Pole Face Flux Director, thedisclosure of which is incorporated herein by reference. Additionalrelated features are also disclosed in the aforementioned commonlyassigned copending application entitled Compressed Natural Gas InjectorHaving Gaseous Dampening For Armature Needle Assembly During Opening.

In addition, as shown in FIG. 4, radial slots in the form recessedsurfaces 18 a are provided in the lowermost surface of inlet connector18 to reduce the effective contact surface area between the armature andthe inlet connector by about one-third of the total cross-sectional areawhich was utilized in prior art conventional injectors. Thisconfiguration provides six coined pads 18 b of about 0.005 mm in height,thus creating six corresponding rectangular shaped radial slots 18 a toprovide fuel flow paths. By reducing, the effective surface area of thelowermost face of the inlet connector 18 as shown, the tendency todevelop an attractive force between the inlet connector 18 and thearmature 14 is significantly reduced to about one-third of its originalvalve, and the ability to tolerate fuel contaminants at the interfacewithout producing an attractive force therebetween is also significantlyincreased. As noted, preferably, the rectangular radial slots 18 a areof a shallow depth, i.e. about 0.05 mm, (i.e., millimeters) in order toprovide the benefit of reducing the inlet connector/armature interfacesurface area while still providing a relatively unobtrusive location forcollection of solid contaminants which are ultimately removed by theflow of gaseous CNG.

As noted, the provision of recessed surfaces 18 a in the lowermostsurface of inlet connector 18 creates raised pads 18 b on the surface,which pads improve the tolerance of the injector to fuel contaminants inseveral ways. The recessed surfaces 18 a may be made by any suitableprocess, but are preferably coined. The first effect is to reduce thecontact area of the inlet connector at the armature interface, therebysignificantly reducing any attractive force generated therebetween byliquid contaminants such as oil or water. Furthermore, as noted, theradial pads 18 b provide hidden areas between the pads wherecontaminants can collect without affecting the operative working gap 15until being drawn away by the fuel flow. The working gap for gasoline isabout 0.08 mm to about 0.14 mm and about 0.3 mm for compressed naturalgas. In addition, as noted, the provision of the six rectangularrecessed portions in the form of slots 18 a and six raised pads 18 b,each having a generally trapezoidal shape, on the inlet connector,provide a unique fuel flow path past transversely through the workinggap 15 as shown at 56 in FIG. 5 and allow for the control of the fuelflow around and through the armature by controlling the pressure losses.

Also, by controlling the sizes of the recessed surfaces 18 a and raisedpads 18 b, and the various apertures 58, 60, 66 in the armature and thevalve body as will be described—as well as the numbers and combinationsof such openings—the fuel flow can be controlled over at least threeflow paths and pressure losses can also be controlled. For example, asmall pressure differential across the armature while fully open,assists spring 30 during breakaway upon closing the provides dampeningon opening impact. The additional fuel flow path also reduces thepossibility of contaminants collecting above upper guide 36 as shown inFIG. 2. In summary, numerous combinations of apertures and sizesthereof—as well as slots and pads on the fuel inlet connector—can bemade to direct the gaseous fuel flow in any desired manner which is bestfor optimum fuel burning and engine application.

Referring now to FIGS. 5 and 6 in conjunction with FIGS. 1-3, there isillustrated still another significant improvement which renders thepresent fuel injector assembly more fully capable of operation with CNG.In injectors which were used with relatively contaminant free liquidfuels the fuel would pass through the filter down through the inletconnector into the armature and out an opening positioned relativelyclose to the lowest portion of the armature which was locatedsubstantially immediately above the valve aperture. In the presentstructure there is provided a relatively diagonally oriented aperture 58in the armature as shown in FIG. 5, which directs the CNG flowtherethrough and downwardly toward valve aperture 41 for entry into theintake manifold of the internal combustion engine.

As shown in FIG. 5, aperture 58 forms a generally acute angle withlongitudinal axis A—A of the fuel injector 10. In addition, the armatureof the present invention provides at least one side opening 60 which isgenerally transverse to the longitudinal axis A—A, to permit fuelflowing downwardly through the center of the armature to be directedsidewardly out of the armature and thereafter downwardly toward thevalve aperture 41 shown in FIG. 1. In the embodiment shown in FIG. 1,aperture 60 is generally horizontal, but may be oriented at an acuteangle to the longitudinal axis if desired. Aperture 58 is not shown inthe cross-sectional view of armature 14 in FIG. 1. The fuel flowingthrough aperture 60 is indicated by the flow lines 62 and the fuelflowing through aperture 58 is indicated schematically by flow lines 64.Optionally several additional horizontal apertures 60 may be provided inthe armature at different radial locations thereabout, or alternativelyas shown, one aperture 60 may be provided, depending upon the fuel flowpattern sought in each particular instance. It can be seen that the fuelflow from the fuel inlet connector 18 is divided into three paths, afirst path expanding across working gap 15, a second path throughaperture(s) 60, and a third path through aperture(s) 58. The first pathextends between the armature 14 and the magnetic coil 28 and isultimately joined by the second flow path passing through aperture(s)60.

It can also be readily appreciated that the diameters of each aperture58, 60 can be varied to direct the fuel flow in any predetermineddesired direction. For example, by reducing the size of apertures 58, 60fuel will be encouraged to flow with increased volume cross the workinggap 15. Alternatively, increasing the diameter of apertures 58, 60 willattract greater volume of fuel through those apertures and therebyreduce the fuel flow across the working gap. It has also been found thatthe diameters of the apertures 58, 60 and the numbers and locations ofsuch apertures affect the dampening characteristics of the valve needle16, both upon opening and upon closing. Accordingly, the diameter offuel flow apertures 58, 60 and the numbers, locations, and orientationsof such apertures will depend upon the desired volumetric flowcharacteristics and desired flow patterns in each instance; however,diameters within the range of 1-2 mm have been found to be preferable.

Referring now to FIG. 6, a valve body 34 is also provided with centralfuel flow opening 35 and several diagonally oriented fuel path apertures66 which are intended to receive the CNG fuel flowing from the first andsecond flow paths from the working gap 15 and aperture(s) 60 along thesides of the armature 14 and to redirect the fuel downwardly toward thevalve aperture 41. When the needle 16 is lifted, the fuel is permittedto enter aperture 41 and thereafter directed into the intake manifold ofthe engine, which is not shown in the drawings. Fuel flowing along thethird flow path through aperture(s) 58 lead directly toward aperture 41.It has been found that the unique provisions of the apertures 58 and60—as well as rectangular radial slots 18 a on the inlet connectorlowermost face—create a fuel flow pattern which induces the CNG to flowin the manner shown by the fuel flow lines at 56 61 and 64 in FIG. 5 andsuch fuel flow lines actually create ideal pressure conditions to avoidcausing the armature to be attracted to the inlet connector. Thus theattractive forces between the armature and inlet connector are minimizedby the several factors mentioned, namely the elimination of the tendencyof the oil and contaminates to accumulate in the space 15 locatedbetween the armature and the inlet connector, the reduction of theeffective inlet connector/armature interface area by provision of radialpads on the face of the inlet connector, and the unique CNG flow patterwhich creates a force free environment between the inlet connector andthe armature.

As indicated, alternatively, apertures 60 may be provided in severallocations about the circumference of the armature, and apertures 58 maybe provided in several locations thereabout. Also their angularorientations may be varied. However, it has been found that a singleaperture on each side, as shown is sufficient to produce the desiredflow path and the force free environment. Also, as noted, it should benoted that the diameter of each aperture can be altered in order toprovide control of the fuel pressures and flow patterns in the areassurrounding the inlet connector, the armature, and the valve body, so asto provide a predetermined fuel flow pattern throughout the injector asmay be desired. This feature is more fully disclosed in theaforementioned commonly assigned, copending application entitledCompressed Natural Gas Injector Having Gaseous Damping For ArmatureNeedle Assembly During Opening.

It should also be noted that the presence of the diagonally orientedfuel flow apertures 66 in valve body 34 eliminates the problems of priorart injectors wherein debris and contaminants would accumulate in thearea of the upper valve guide 36, causing abrasive action andintermittent guidance between the upper guide 36 and the armature 14.Thus, the provision of the diagonally oriented apertures 66 in valvebody 34 encourage the flow of CNG past the area surrounding the upperguide 36 and eliminate any accumulation tendencies for contaminants inthe area of upper guide 36.

Referring now to FIGS. 7 and 8 there is shown a comparison between thevalve needle seat of the type used in earlier developments, and the lowrestriction valve needle seat constructed according to the presentinvention.

In FIG. 7, there is illustrated a tip portion 17 of a valve needle 16 ofthe type shown in FIGS. 1 and 2, in combination with a valve needle seat82 of the type used in earlier developments. Lower needle guide 80 isshown in cross-section in combination with the tip portion 17 of needle16, and is also shown in FIG. 9. As can be seen, the valve needle seat82 has a frusto-conically shaped needle rest, all sides of which form anangle of approximately 90°, and a valve orifice 81 which, together withthe needle rest surfaces 84, 86 form a funnel like arrangement throughwhich the gaseous fuel must pass. Although needle rest surfaces 85, 86actually form part of the same frust-conical surface, they are referredto separately for convenience of the description.

In contrast to the valve needle seat shown in FIG. 7, the valve needleseat 40 constructed according to the present invention is shown in FIG.8. Referring to FIG. 8, it can be seen that the valve needle seat 40includes frusto-conical valve needle seat surface 88, which iscontinuous and which forms an angle of approximately 90° incross-section. However, valve needle seat 40 also includes an arcuatecircular annular groove 92 having an arcuate surface 94 as shown, whichconnects the vertical surface and the horizontal surface of the groove92 as shown. The function and purpose of groove 92 will best beappreciated by referring to FIG. 9, which illustrates a plan view oflower valve needle guide 80.

Referring now to FIG. 9, lower valve needle guide 80 includes arcuateapertures 96 which permit the flow of gaseous fuel therethrough forpassage through valve aperture 41. Although arcuate apertures 96 arerelatively large, the lower valve needle guide nevertheless tends topresent a restriction to the passage of gaseous fuel thereby.Accordingly, in the structure shown in FIG. 7, as the needle 16 movesdownwardly toward the valve seat 82 to pinch the flow at the contactpoints 43, immediately prior to actual contact, the pressuredifferential across the contact points 43 is substantial in that thepressure between the lower valve guide and the contact points 43 issubstantially greater than the pressure on the opposite side of thecontact points 43 just prior to contact being completed. In fact, thepresence of the lower needle guide 80 tends to increase the pressure inthe zone immediately above the contact points 43. Although “contactpoints 43” are referred to as “points,” they each in fact are points onthe same circle formed by the points of tangency between the arcuateneedle contact surface and the needle rest surface. However, they arereferred to separately for convenience of the description.

In contrast thereto, as shown in FIG. 8, the presence of the annulargroove 92 which is provided in the needle valve seat tends to reduce thedifferential pressure across the seal points 43 by providing additionalvolumetric space between the lower needle guide 80 and the valve seat40. Thus, the pressure differential across the seal points 43 issomewhat reduced thereby reducing the flow reducing pressure lossesotherwise occurring across the point of contact between the needle 16and the valve seat 40. Since such pressure losses tend to reduce thefuel flow passing through the injector, the provision of the uniquevalve seat 40 as shown in FIG. 8 has been found to avoid such reductionin fuel flow which occurs normally as a result of such pressure losses.This factor increases the energy flow into the engine withcorrespondingly increased efficiency.

Although the invention has been described in detail with reference tothe illustrated preferred embodiments, variations and modifications maybe provided within the scope and spirit of the invention as describedand as defined by the following claims.

What is claimed is:
 1. An electromagnetically operable fuel injector fora gaseous fuel injection system of an internal combustion engine, saidinjector having a generally longitudinal axis, which comprises: (a) aferromagnetic core; (b) a magnetic coil at least partially surroundingthe ferromagnetic core; and (c) an armature magnetically coupled to saidmagnetic coil and being movably responsive to said magnetic coil, saidarmature actuating a valve closing element which interacts with a fixedvalve seat of a fuel valve and being movable away from said fixed valveseat when said magnetic coil is excited, said fixed valve seat defininga central fuel opening and a generally annular groove adjacent saidcentral fuel opening, said armature having a generally elongated shapeand a generally central opening for axial reception and passage ofgaseous fuel from a fuel inlet connector positioned adjacent thereto,said fuel inlet connector and said armature being adapted to permit afirst flow path of gaseous fuel between armature and said magnetic coilas part of a path leading to said fuel valve, said fuel inlet connectoris positioned above said armature and is spaced from said armature by aworking gap, wherein said fuel inlet connector comprises an upper endportion adapted for reception of gaseous fuel from a fuel source, and alower end portion for discharging gaseous fuel, said lower end portionhaving a lower surface which faces an upper surface of said armature,said lower surface of said fuel inlet connector having a plurality ofradially extending raised pads defined thereon, said pads havingrecessed portions therebetween to permit fuel to flow therethrough andacross said working gap defined between said fuel inlet connector andsaid armature.
 2. The electromagnetically operable fuel injectoraccording to claim 1, further comprising at least one first fuel flowaperture extending through a wall portion of said armature to define asecond flow path of gaseous fuel as part of a path leading to said fuelvalve.
 3. The electromagnetically operable fuel injector according toclaim 2, wherein said armature defines at least one second aperture in awall portion thereof to define a third flow path of gaseous fuel as partof a path leading to said fuel valve.
 4. The electromagneticallyoperable fuel injector according to claim 3, wherein said at least onesecond aperture is oriented at a generally acute angle with respect tothe longitudinal axis.
 5. The electromagnetically operable fuel injectoraccording to claim 4, wherein said fuel inlet connector and saidarmature are spaced to define a working gap therebetween and are adaptedto permit said first flow path of gaseous fuel within said working gap.6. The electromagnetically operable fuel injector according to claim 5,further comprising a valve body positioned downstream of said armatureand having at least one aperture in a wall portion thereof for receptionof fuel from at least two of said flow paths of gaseous fuel from saidarmature and said fuel inlet connector.
 7. The electromagneticallyoperable fuel injector according to claim 6, further comprising a valvebody shell at least partially surrounding said armature and said valvebody, said valve body shell defining a radial space with said armaturefor passage of said first flow path of gaseous fuel between saidarmature and said valve body shell.
 8. The electromagnetically operablefuel injector according to claim 7, wherein said fuel inlet connector ispositioned above said armature and is spaced from said armature by aworking gap, said fuel inlet connector defining a through passage fordirecting fuel toward said armature and said fixed valve seat.
 9. Anelectromagnetically operable fuel injector for a compressed natural gasfuel injection system of an internal combustion engine, said injectorhaving a generally longitudinal axis, which comprises: (a) aferromagnetic core; (b) a magnetic coil at least partially surroundingsaid ferromagnetic core; (c) an armature magnetically coupled to saidmagnetic coil and movably responsive to said magnetic coil, saidarmature having a first upper end face and a lower end portion; (d) avalve closing element connected to said lower end portion of saidarmature and interactive with a fuel valve having a fixed valve seat toselectively permit fuel to pass through said valve seat as said valveclosing element is moved to a valve open position by said armature, saidfixed valve seat having a generally frusto-conically shaped portionsurrounded by an adjacent circular shaped annular groove to reduce thepressure differential occurring across the valve closing element andsaid fixed valve seat upon closing said fuel valve; (e) a fuel inletconnector extending in a generally longitudinal direction above saidarmature and defining a path for fuel to enter said inlet connector andto be directed toward said armature, said fuel inlet connector having alowermost end portion having a lowermost surface spaced above saidarmature to define a working gap through which said armature ismoveable; and (f) said armature having a fuel reception portion forreceiving a fuel directed from said fuel inlet connector, said armaturefurther defining a generally axial fuel passage, wherein at least afirst fuel flow aperture extends through a wall portion of said armaturefor directing fuel from said fuel inlet connector through said generallyaxial fuel passage and into said aperture toward said fixed valve seatfor entry into an air intake manifold of the engine, said fuel flowaperture being oriented generally transverse to said longitudinal axis,and wherein said armature further defines at least a second fuel flowaperture extending through a lower portion thereof and oriented at anacute angle with said longitudinal axis, and positioned for directingfuel therethrough toward said fixed valve seat.
 10. Theelectromagnetically operable fuel injector according to claim 9, whereinsaid lowermost surface of said fuel inlet connector and said armatureare adapted to permit gaseous fuel to flow across said working gap andbetween said armature and said magnetic coil whereby at least three fuelflow paths are permitted.
 11. The electromagnetically operable fuelinjector according to claim 10, wherein said lowermost end portion ofsaid fuel inlet connector has a generally chamfered configuration alongthe lowermost outer surface thereof.
 12. The electromagneticallyoperable fuel injector according to claim 11, wherein said generallychamfered portion of said fuel inlet connector has a generally arcuatecross-section.
 13. The electromagnetically operable fuel injectoraccording to claim 12, wherein said valve closing element is a valveneedle adapted for selective engagement and disengagement with saidfixed valve seat.
 14. The electromagnetically operable fuel injectoraccording to claim 13, wherein said valve needle is attached to saidarmature by crimped portions of said armature.
 15. Theelectromagnetically operable fuel injector according to claim 14,wherein a fuel filter is positioned at an upper end portion of said fuelinlet connector for filtering fuel prior to reception by said fuel inletconnector.
 16. The electromagnetically operable valve according to claim15, wherein said fuel inlet connector includes a lower surface portionhaving a plurality of radially extending grooves defining acorresponding plurality of radially extending raised pads so as toreduce the effective surface area of said lower surface portion of saidfuel inlet connector facing said armature to thereby permit the gaseousfuel to flow generally transversely in said working gap, said transversefuel flow thereby preventing accumulation of contaminants in saidworking gap.
 17. The electromagnetically operable fuel injectoraccording to claim 16, wherein said generally radially extending padshave a generally trapezoidal shape.
 18. An electromagnetically operablefuel injector for a gaseous fuel injection system of an internalcombustion engine, said injector having a generally longitudinal axis,which comprises; (a) a ferromagnetic core; (b) a magnetic coil at leastpartially surrounding the ferromagnetic core; (c) an armaturemagnetically coupled to said magnetic coil and being movably responsiveto said magnetic coil, said armature actuating a valve closing needlehaving a generally spherically shaped fuel sealing tip portion whichinteracts with a fuel valve having a fixed valve seat and being movableaway from said fixed valve seat when said magnetic coil is excited, saidfixed valve seat having a generally annular sealing surface having agenerally frusto-conical cross-sectional shape for engaged reception ofsaid generally spherically shaped needle tip portion, said generallyannular sealing surface defining a central opening for passage ofgaseous fuel to a fuel intake manifold, and a generally circular annulargroove adjacent said sealing surface to provide increased volumetricspace adjacent said fixed valve seat for reception of gaseous fuel tothereby reduce the pressure loss across said needle and said valve seatupon closure thereof, said armature having a generally elongated shapeand a generally central opening for axial reception and passage ofgaseous fuel from a fuel inlet connector positioned adjacent thereto;and (d) at least one first fuel flow aperture extending through a wallportion of said armature for reception of gaseous fuel flowing from saidinlet connector and for directing the gaseous fuel to a valve body atleast partially surrounding said armature, said valve body having agenerally elongated central opening for reception of substantially allof the gaseous fuel from said armature, wherein at least a first fuelflow aperture extends through a wall portion of said armature fordirecting fuel from said fuel inlet connector through said generallyaxial fuel passage and into said aperture toward said fixed valve seatfor entry into an air intake manifold of the engine, said fuel flowaperture being oriented generally transverse to said longitudinal axis,and wherein said armature further defines at least a second fuel flowaperture extending through a lower portion thereof and oriented at anacute angle with said longitudinal axis, and positioned for directingfuel therethrough toward said fixed valve seat.
 19. Anelectromagnetically operable fuel injector for an internal combustionengine, said injector defining a generally longitudinal axis, whichcomprises: a) an outer housing; b) a fuel inlet connector positioned inthe upper end portion of said outer housing, said fuel inlet connectorhaving an uppermost end portion for reception of fuel therein and alowermost end portion for discharge of fuel therefrom: c) an armaturepositioned below said fuel inlet connector and defining a generallyaxial elongated central opening to receive fuel flow from said fuelinlet connector, said armature having an uppermost end portionpositioned below said lowermost end portion of said fuel inlet connectorto define a working gap, and a lowermost end portion having a valveclosing element positioned thereon for interaction with a fuel valve toselectively permit fuel to flow through said valve aperture when saidarmature is selectively moved upwardly toward said fuel inlet connector,said fuel valve defining a fixed valve which surrounds a central fuelopening for passage of gaseous fuel, said fixed valve seat further beingsurrounded by a generally circular annular groove adjacent thereto forreception of gaseous fuel passing therethrough so as to reduce thegaseous pressure loss across said valve during closure thereof; d) saidfuel inlet connector having a lowermost end portion having a lowermostsurface which faces said uppermost end portion of said armature, saidlowermost end portion of said fuel inlet connector having a plurality ofradially extending grooves separated by a corresponding plurality ofradially extending raised pads to reduce the effective contact surfacearea between said inlet connector and said armature and to permit fuelto flow from said fuel inlet connector across said working gap; e) amagnetic coil system for moving said armature and said valve closingelement away from said fixed valve seat and toward said fuel inletconnector when said magnetic coil system is energized so as to permitfuel to flow through said fixed valve seat; f) a resilient device tobias said armature and said valve closing element to move toward saidfixed valve seat when said magnetic coil system is deenergized; g) atleast one first aperture extending through a wall portion of saidarmature for receiving fuel flow from said fuel inlet connector anddirecting said fuel flow from said generally elongated central openingof said armature toward said fixed valve seat, said at least oneaperture being generally transverse to the longitudinal axis; and h) atleast one second aperture extending through a wall portion of saidarmature for receiving fuel flow from said fuel inlet connector anddirecting said fuel flow toward said fixed valve seat, said secondaperture being oriented at a generally acute angle relative to thelongitudinal axis for directing fuel from said generally central openingoutwardly of said armature and downwardly toward said fixed valve seat.20. The electromagnetically operable fuel injector according to claim19, wherein said valve closing element is a generally elongated valveneedle having a spherically shaped end portion and configured andadapted to engage a frusto-conically shaped fixed valve seat to closesaid valve, and movable therefrom to open said valve to permit fuel topass therethrough toward the intake manifold of the internal combinationengine.
 21. The electromagnetically operable fuel injector according toclaim 20, wherein said valve needle is connected to the lower endportion of said armature by crimped portions.
 22. Theelectromagnetically operable fuel injector according to claim 21,wherein said resilient device is a coil spring in engagement at one endwith said fuel inlet connector and at the other end with said armatureto bias said armature downwardly toward said valve seat.
 23. Theelectromagnetically operable fuel injector according to claim 22,wherein said armature includes at least two of said first aperturesextending through wall portions thereof and generally transverse to thelongitudinal axis for receiving fuel from said generally axial elongatedcentral opening.
 24. The electromagnetically operable fuel injectoraccording to claim 23, wherein said armature defines a plurality of saidfirst apertures for receiving fuel from said generally axial elongatedcentral opening.
 25. The electromagnetically operable fuel injectoraccording to claim 24, wherein said armature defines at least aplurality of said second apertures, each said second apertures extendingat a generally acute angle to the longitudinal axis to receive fuel fromsaid generally central opening.
 26. A method of directing gaseous fuelthrough an electromagnetically operable fuel injector fuel injector fora fuel system of an internal combustion engine, said injector having agenerally longitudinal axis, and including a fuel inlet and portion anda fuel outlet end portion, a fuel inlet connector positioned at saidfuel inlet end portion and having a fuel inlet end portion and a fueloutlet end portion, an armature positioned adjacent said fuel outlet endportion of said fuel inlet connector, said fuel inlet connector, saidarmature being spaced from said fuel inlet connector to define workinggap to permit movement of said armature toward and away from said fuelinlet connector to selectively open and close a fuel valve by providingupward and downward movement of a valve closing element to selectivelypermit gaseous fuel to pass therethrough to an air intake manifoldcomprising: a) directing the gaseous fuel to pass axially through saidfuel inlet connector; b) directing the gaseous fuel to pass from saidfuel inlet connector to said generally elongated central opening of saidarmature in a axial direction toward said fuel valve; and c) providing avalve seat with an annular groove adjacent a sealing surface, theannular groove receiving fuel so as to reduce pressure losses acrosssaid fuel valve during closure thereof.
 27. A method of directinggaseous fuel through air electromagnetically operable fuel injector fora fuel system of an internal combustion engine, said injector having agenerally longitudinal axis, and including a fuel inlet end portion anda fuel outlet end portion, a fuel inlet connector positioned at saidfuel inlet end portion and having a fuel inlet end portion and a fueloutlet end portion, and armature positioned adjacent said fuel outletend portion of said fuel inlet connector and having a generally centralelongated opening for reception of fuel from said fuel inlet connector,said armature being spaced from said inlet connector to define a workinggap to permit movement of said armature toward and away from said fuelinlet connector to selectively open and close a fuel valve having avalve seat and a fuel passage aperture by providing upward and downwardmovement of a valve needle with respect to a needle/seat interface topermit gaseous fuel to pass through said aperture toward an intakemanifold, comprising: a) directing the gaseous fuel to pass axiallythrough said fuel inlet connector; b) directing the gaseous fuel to passfrom said fuel inlet connector to said generally elongated centralopening of said armature in an axial direction toward said fuel valve;c) directing at least a portion of the fuel flow from said fuel inletconnector to said armature to flow generally transversely across saidworking gap; d) diverting at least a portion of the flow of gaseous fuelpassing through said armature to flow in a direction away from saidaxial direction; and e) providing a valve seat with an annular grooveadjacent a sealing surface, the annular groove receiving fuel so as toreduce pressure losses across said fuel valve during closure thereof.